1. Field of the Invention
The present invention relates to a marine propulsion system, and, more specifically, to a water jet propulsion system utilizing a fluid flow amplifier.
2. Description of the Prior Art
Power driven water craft are generally propelled by either multibladed propellers or water jet drivers. While more exotic propulsion systems are available, they are not in widespread commercial use. Propeller and water jet drivers are relatively inefficient propulsion systems and are extremely energy intensive.
Marine propulsion systems basically operate over a widespread speed range. The drive efficiency of the marine propulsion system varies over the speed range to which the system is applied. The hull efficiency also varies over the marine propulsion speed range in a complex relationship between the two. Combining propulsion and hull efficiency variations results in combinations that have peak efficiency only at a single point or within a very narrow speed range. Various devices may be utilized to counteract this problem, such as variable pitch propellers, trim and tilt adjustments for thrust alignment, etc. These devices add complexity and cost to the system and their operation is most often subjectively controlled by the operator. Therefore, efficiency is related to the operator's skill in controlling the effect of these devices on the propulsion and hull system variations.
Fluid flow amplifiers are well-known in the fluid jet propulsion field. Such devices are used to move large volumes of fluid with relatively small input flows. Venturi ejectors and Canoda effect devices are fluid flow amplifiers which are known in the art. These devices generally make use of a high velocity, low volume stream to act upon and accelerate a larger fluid stream. The energy of the high velocity primary fluid stream is used to accelerate and eject a much larger volume of secondary fluid at an increased velocity, which velocity is lower than that of the low volume primary fluid stream. Fluid flow amplifiers, however, are subject to the same limitation as the conventional propeller and water jet driver propulsion systems of only delivering peak efficiency from an optimum combination of the propulsion and hull efficiency variation which lies only in a very narrow speed range.